I've just been having a look at them as I tried to design my own rules to accomplish what you wanted. Having had a reasonable stab at it I decided they were about as inelegant as an inelegant thing could be.So I looked up WBH rules to see what they'd done. Here they are:
I like the simplicity of this - although it doesn't quite do what you want it to WRT to GOV and LAW being affected by one another (or TL for that matter).I like that it says 'major' powers so you always have the option of lots of minor ones if you wish.Not so fond of it only allowing 1D-1 powers as it would be harder to replicate Earth's 200+ (although obviously a huge number would be minor).
My scheme didn't have '7' as a GOV type rerolled but in effect further subdivided that country so that lots of minor countries were possible.I also note they bypass the whole 'apportion the pop between countries' by just making a referee decision about it.
Having had a play with this, I would either use WBH as is for balkanized worlds, or just design each one by hand for whatever effect I wanted to achieve. Unless someone can come up with something a lot more elegant than my poor effort!